The present invention relates to an optical scanner that allows an adjustment for compensating a scan line bow from either side of an optical element, and to an image forming apparatus provided with the optical scanner.
In electrophotographic image forming apparatus, an electrostatic latent image is formed using an optical scanner to cause a scan line to irradiate a photo conductor. In the optical scanner, a plurality of optical elements (f-theta lenses) are equipped; and the scan line, after transmitting the plurality of the f-theta lenses, arrives on the photo conductor.
Therefore, in order for a scan line to irradiate accurately a predetermined position on the photo conductor, it is required for the f-theta lenses to be capable of transmitting the scan line in high accuracy.
However, there has been a problem that scan line bow occurs when the scan line transmits the f-theta lens because internal structure thereof changes in cooling process after it was molded.
Then, a technique has been disclosed in which adjusting screws are provided at three places in total along the longitudinal direction of the f-theta lenses including the neighborhood of its middle point, thereby allowing an adjustment on push-in depth of each of the screws in order to deform the f-theta lenses in such a manner that the scan line bow is reduced (for example, refer to Japanese Patent Unexamined Publication No. 2007-065500 bulletin).
However, the technique as described in the Japanese Patent Unexamined Publication No. 2007-065500 bulletin can deform the f-theta lens only from a single side thereof. Therefore, in a case where a scan line bow cannot be reduced unless the side is opposite to the side where adjusting screws are disposed is pressed, it was necessary for the f-theta lens to be removed from a holder, to be caused to make a half-turn, and then to be mounted on the holder once again.
Then, in view of the problem as described above, the present invention is directed to providing an optical scanner that allows an adjustment to a scan line bow from either face side of an optical element.